Numerous telescopic members are known in which the retracted position is defined by an internal abutment, e.g. actuators or undercarriage shock absorbers for aircraft.
In the more specific circumstance of shock absorbers, it is often necessary to define an abutment in shortening, since such shock absorbers are also used for retracting the undercarriage, the internal abutment thus serving to define the retracted position of the undercarriage.
Nevertheless, the working stroke defined by the abutment can be shorter than the stroke needed to absorb landing energy in the event of a hard landing.
Telescopic members are known that have an overridable abutments. In particular, it is known to use an abutment piece disposed in the end of the shock absorber with the rod of the shock absorber coming to bear thereagainst on reaching the abutment position. When the rod presses with a force above a predetermined threshold, that causes the abutment piece to buckle, thereby providing the rod with overtravel beyond its retracted position.
Nevertheless, such abutment pieces are of complex shape in order to enable buckling to be initiated, and because of manufacturing dispersion, it is very difficult to ensure that the buckling threshold is complied with.